剑指offer系列57---整数中1出现的次数

 1 package com.exe11.offer;
 2 /**
 3  * 【题目】求出1~n的整数中1出现的次数.
 4  * @author WGS
 5  *
 6  */
 7 public class NumberOf1 {
 8 
 9     public int getNumberOf1Between1AndN(int n){
10         if(n<=0) return 0;
11         if(n<=9) return 1;
12         int count=0;
13         for(int i=1;i<=n;i++){
14             count+=getCount(i);
15         }
16         return count;
17         
18     }
19     private int getCount(int n) {
20         int numberOf1=0;
21         int flag=0;
22         while(n!=0){
23             flag=n%10;
24             if(flag==1)
25                 numberOf1++;
26             n=n/10;
27         }
28         return numberOf1;
29     }
30     public static void main(String[] args) {
31         NumberOf1 n=new NumberOf1();
32         int num=n.getNumberOf1Between1AndN(7);
33         System.out.println(num);
34 
35     }
36 
37 }